Exploration for and production of hydrocarbon based energy deposits has often required that people and equipment operate in challenging and potentially hazardous environments around the world. As hydrocarbon deposits become more difficult to find, more exploration and production activities are occurring in bodies of water including oceans and seas. Offshore hydrocarbon exploration and production requires that expensive rigs or vessels be semi-permanently located in bodies of water. Many bodies of water are subject to dramatic and sudden changes in weather. More notorious examples of such changes include storms such as tropical storms, typhoons, and hurricanes.
Offshore rigs are usually supported structurally from the sea floor (e.g. jack-up rigs and island rigs) or are supported by buoyant structures (e.g. semi-submersibles, spars, ships). Some hybrid designs exist. Most rigs are moored to the sea floor by anchors and mooring lines in order to resist lateral rig movement. Such rigs are usually manned either around the clock or intermittently in order to monitor and maintain rig systems and operations.
When a storm approaches an offshore rig the safety of the rig crew becomes a primary issue. The condition and location of the rig are also at issue. As a storm approaches the rig crew is evacuated either by boat or helicopter and the rig is left unmanned or partially unmanned. Events that occur as the storm draws near to and impacts the rig go largely unmonitored. If standard rig communications go down before an evacuation can occur, the situation for the rig crew becomes critical. If the rig is evacuated before a storm arrives then the condition and location of the rig become unknown until some time after the storm has passed.
If the storm has damaged critical rig systems including mooring lines, such damage can not be detected until after the storm has passed. In many cases a rig that has been hit or almost hit by a storm can not even be readily located because the mooring lines have been broken and the rig has drifted. Rigs have been blown off location by hundreds of miles in some instances. Such drifting rigs create a hazard separate from that of the storm in that the rig may actually impact another vessel or structure. An ability to locate a drifting rig and advance warning of the status and course of such a rig is needed. So that design insight may be gained for the future, an ability to analyze events leading up to the loss of a rig at sea is also needed.
Methods for tracking things such as automobiles, boats and airplanes have been devised. Devices such as Lo-Jack (registered) have been marketed for tracking stolen automobiles. When activated, that device sends a radio signal that can be received by a tracking device. Such a device does not provide exact automobile location; rather it provides location information relative to the tracking receiver. The Lo-Jack device is described in U.S. Pat. Nos. 4,908,629, 4,818,998, and 4,177,466.
A system and method for monitoring a boat are subjects of U.S. Pat. No. 6,469,641. That patent discloses tracking a stolen boat and monitoring certain security and operational parameters related to the boat such as unauthorized entry, bilge pump function, battery charge, and boat location. Such a system for monitoring of a boat does not address parameters relevant to a rig or its environment.
While there are many different types of tracking and monitoring systems including some for marine vessels, none address issues and parameters that are of specific interest regarding an offshore hydrocarbon rig.
Accordingly, there is a need for an invention that facilitates the monitoring of parameters related to an offshore rig and the communication of information related to the offshore rig to a remote location where concerned persons are able to access such information. Such an invention should preferably operate in inclement weather and through periods of rig power interruption.